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A031218
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Largest prime power <= n.
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9
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1, 2, 3, 4, 5, 5, 7, 8, 9, 9, 11, 11, 13, 13, 13, 16, 17, 17, 19, 19, 19, 19, 23, 23, 25, 25, 27, 27, 29, 29, 31, 32, 32, 32, 32, 32, 37, 37, 37, 37, 41, 41, 43, 43, 43, 43, 47, 47, 49, 49, 49, 49, 53, 53, 53, 53, 53, 53, 59, 59, 61, 61, 61, 64, 64, 64, 67, 67, 67, 67, 71, 71
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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The length of the m-th run of {a(n)} is the length of the (m+1)-st run of A000015 for m > 1. - Colin Linzer, Mar 08 2024
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LINKS
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B. Dearden, J. Iiams, and J. Metzger, Rumor Arrays, Journal of Integer Sequences, 16 (2013), #13.9.3.
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PROG
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(PARI) a(n)=if(n<1, 0, while(matsize(factor(n))[1]>1, n--); n)
(Haskell)
a031218 n = last $ takeWhile (<= n) a000961_list
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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